I have a Weatherby Vanguard in .223 caliber. As far as I know, I'm not supposed to use 5.56 ammo in it. But in looking at several web sites, it shows up as .223/5.56 . So now I'm confused. I never would have cared but with the ammo shortage 5.56 is more available. I know the barrel pressures are far greater with the 5.56 ammo. Don't worry, I'm not trying it until I get some good facts from you guys.....send them in please.